More fascinating facts you never knew about smiling:

One smile can give the same level of brain stimulation as 2000 bars of chocolate.

Smiling can be as stimulating as receiving £16,000 in cash.

When you smile others think you are more competent.

Unborn babies smile.

Your smile can be a predictor of how long your marriage lasts.

Read more from Ron Gutman on the power of the smile.